There might be some privacy issue with it. A sophisticated actor might able to correlate the traffic of a hidden service (e.g. your lightning node's onion address) to that of the tor relay, which could expose your lightning node's IP address.

You might also try to find out what your ISPs policy is regarding tor relays and exit nodes. Some might threaten you with shutting down your service. If you surf the web from the same IP address, you might find yourself quickly blocked from a lot of services, and you'll need a personal VPN to make the internet usable for yourself again.

Maybe start with a Tor relay first. Running an exit node is a bit riskier depending on your ISPs policies and local regulation.

Source: I ran a Tor relay from home for years

In practice it would probably be just fine and nothing happens.

In theory Bitcoiners like to isolate everything money related as far as possible. Especially if keys are stored on it. Biggest risk imo is this specific node getting down from too much load.

If you're referring to this: I think he meant Bitcoin Core nodes behind Tor, not nodes of the Tor network (relays or exit nodes). So your running a relay or exit node wouldn't help that.

Tor-Only Bitcoin & Lightning Guide

Guys please STOP running Tor only LN nodes ! You are doing more damage than good to yourself and to the rest of the network! LN is not meant to be run over Tor, especially for a public routing node.

Only for preserving your privacy seperate both of them!!!